This invention relates to compositions and methods for controlled release of agricultural chemicals.
An agricultural chemical, such as a biocide, a chemical hybridizing agent, or a plant growth regulator is applied to a plant, to a seed, or to soil at the beginning of a growing season and must maintain their effectiveness throughout the growing season, which can last for several months. However, the agricultural chemical may be degraded by chemical or biological processes and removed by wind or water from the site of application. As a result, it is necessary to apply high rates of the agricultural chemical to maintain the desired effect over time or to apply the chemical repeatedly during the growing season. However, high rates of certain agricultural chemicals can be phytotoxic to a plant which is sought to be protected (“agronomic plant”) from the disease or pest which the agricultural chemical is meant to control. For example, many fungicides, such as triazole fungicides, can be phytotoxic to the agronomic plant when applied in amounts that are necessary to provide agronomically adequate disease control.
Numerous triazole fungicides have been developed and commercialized. The triazole fungicides are generally characterized as having a 1H-1,2,4-triazole group. Some individual representative triazole fungicides are listed in the table below.
TriazoleCAS RegistryFungicideNumberbitertanol 70585-36-3bromuconazole116255-48-2cyproconazole 94361-06-5difenoconazole119446-68-3epoxiconazole106325-08-0fenbuconazole114369-43-6fluquinconazole136426-54-5flusilazole 85509-19-9flutriafol 76674-21-0hexaconazole 79983-71-4imibenconazole 86598-92-7metconazole125116-23-6myclobutanil 88671-89-0penconazole 66246-88-6propiconazole 60207-90-1tebuconazole107534-96-3tetraconazole112281-77-3triadimefon 43121-43-3triadimenol 55219-65-3triticonazole131983-72-7
Under certain conditions, a triazole fungicide frequently is phytotoxic to the very plant species the fungicide is meant to protect from disease. For example triadimefon can be phytotoxic to ornamental plants (The Pesticide Manual, Eleventh Edition, C. D. S. Tomlin, ed., The British Crop Protection Council, Farnham, Surrey, U.K., 1997, p. 1217); metconazole can cause stunting and yellowing of plants (Id., p. 804); hexaconazole can cause damage to McIntosh apples (Id., p. 675); difenoconazole can cause chlorosis in wheat (Id., p. 390); and bitertanol can cause damage to fruit crops (Id., p. 132).
Controlled release of a pesticide has occasionally been used as a method of controlling phytotoxicity of the pesticide to the beneficial plant species. Patents and published patent applications disclosing various controlled-release formulations include each of the following individual disclosures.                U.S. Pat. No. 4,172,119.        U.S. Pat. No. 4,915,947.        U.S. Pat. No. 5,225,278.        U.S. Pat. No. 5,277,979.        U.S. Pat. No. 5,725,869.        European Patent Publication No. 0 004 758-A2.        European Patent Publication No. 0 018 119-A1.        European Patent Publication No. 0 763 510-A1.        PCT Patent Application No. WO 88/08300.        